MFC r355581:
Avoid access to stale ip pointer and call UPDATE_POINTERS() after PULLUP_LEN_LOCKED(). PULLUP_LEN_LOCKED() could update mbuf and thus we need to update related pointers that can be used in next opcodes. Reported by: Maxime Villard <max at m00nbsd net>
NOTE: this commit also adds UPDATE_POINTERS() stub macro, that originally
is part of r345166 commit that was not merged.